1. Field of the Invention
The present invention relates to a spread illuminating apparatus used as an illuminating means for signboards, various kinds of reflection-type display devices and the like, and more particularly to a spread illuminating apparatus used as an illuminating means for a liquid crystal display device.
2. Description of the Related Art
A demand for a liquid crystal display device as a display device mainly for computers has been increasing since the liquid crystal display device which operates with low power consumption is characterized by being low profile and lightweight. Since a liquid crystal which is a component of the liquid crystal display device does not emit light by itself unlike a light emitting element such as a cathode-ray tube, an illuminating means for viewing an image is required. In particular, in the recent demand for lower profile, there is a growing tendency to employ a thin plate-like spread illuminating apparatus of side light type (light conductive plate type) as an illuminating means for the liquid crystal display device.
An example of such a side light type spread illuminating apparatus is shown in FIGS. 7 to 12.
In FIGS. 7 and 8, this spread illuminating apparatus 1 is generally constituted such that a bar-like light source 3 is disposed close to one end surface 2a of a transparent substrate (a guide plate) 2 made of a light-transmissible material. A liquid crystal display device (not shown) is disposed on a lower surface side of the transparent substrate 2, and this spread illuminating apparatus 1 is used as an auxiliary illumination for the liquid crystal display device.
The transparent substrate 2 is formed in a so-called wedge-shape, in which as the distance from the end surface 2a increases, the thickness of the transparent substrate 2 gradually degreases.
The light source 3 is generally composed of a light conductive member (a guide rod) 4 made of a bar-like transparent material disposed close to and along the end surface 2a of the transparent substrate 2, an LED 6 (a spot-like light source) which is disposed facing one end part 4a of the light conductive member 4 and mounted on an FPC 5 (a printed circuit board) made of an insulating material, and a light reflection plate 7 disposed facing the other end part 4b of the light conductive member 4.
An optical path conversion means 8 is provided on an opposite side surface 4d (a second surface of the light conductive member) of a surface 4c (a first surface of the light conductive member) facing the transparent substrate 2 on the light conductive member 4. The optical path conversion means 8 is composed of grooves 8a each of which is substantially triangular in section, and flat portions 8b each of which is formed between two adjacent grooves 8a. Accordingly, the light rays from one end part 4a of the light conductive member 4 are uniformly radiated on the first surface 4c although the LED 6 is disposed on one end part 4a. 
A light reflection pattern 9 composed of grooves 9a and flat portions 9b is formed on one surface (an upper part in FIG. 7, hereinafter, referred to as xe2x80x9cupper surfacexe2x80x9d) of the transparent substrate 2 so that the brightness is substantially uniform at any position of the transparent substrate 2 irrespective of the distance from the light conductive member 4.
The LED 6 is substantially rectangular, and a groove-shaped recess 20 extending in the vertical direction is formed in a substantially center part of the surface facing an abutting surface on the light conductive member 4.
The LED 6 has solder S applied to both ends 6a and 6b positioned to be aligned in a direction orthogonal to a longitudinal direction of the light conductive member 4 while disposed facing one end part 4a of the light conductive member 4 as shown in FIGS. 7, 10 and 11, and a terminal (not shown) is electrically connected to a copper foil (not shown) provided on the FPC 5, and mounted on the FPC 5 in this condition.
The FPC 5 is composed of a substantially rectangular FPC body 5a with the LED 6 or the like mounted thereon, and an FPC riser wall 5b formed on one end part of the FPC body 5a in a rising manner. The FPC rising wall 5b faces the LED 6, and is interposed between the LED 6 and a frame riser plate 10b as described below, so that the solder S is prevented to be short-circuited to a metal lower frame 10 (the frame riser plate 10b).
As shown in FIGS. 7, 9, 10 and 11, this spread illuminating apparatus is further provided with the metal frame (the lower frame 10) disposed on the lower surface side of the FPC 5, and a substantially plate-like frame (an upper frame 11) disposed facing the FPC 5 across the light conductive member 4, and holds the transparent substrate 2 and the light source 3. The lower frame 10 is substantially composed of a plate-like main body (a lower main body 10a) facing the lower face of the FPC 5 and extending along the light conductive member 4, and a riser plate (the frame riser plate 10b) substantially orthogonal to the lower main body 10a and rising from one end part (the right side in FIG. 10) of the lower main body 10a. The other end part (the left side in FIG. 10) of the lower main body 10a and the transparent substrate 2 are fixed to each other (in a condition where a holding part not shown in the figure is provided), allowing the LED 6 to be pressed toward the light conductive member 4 by the frame riser plate part 10b as described below.
The lower frame 10 allows the frame riser plate part 10b facing one end face 4a of the light conductive member 4 via the FPC riser wall part 5b, and presses the LED 6 toward the light conductive member 4 via the FPC riser wall part 5b. 
Since the lower frame presses the LED 6 toward the light conductive member 4, a coupling efficiency between the light conductive member 4 and the LED 6 is improved, and a variance in tolerance of members is absorbed thereby.
The spread illuminating apparatus is requested to tightly attach the light conductive member and the LED to each other in a reliable condition to obtain excellent light characteristics, and accordingly to improve the coupling efficiency between the light conductive member and the LED. However, in the conventional technology, the LED 6 is pressed toward the light conductive member 4 via the FPC 5 (the FPC riser wall 5b), and thus, no large pressure is obtained, and accordingly, the improvement in the coupling efficiency has been restricted.
In addition, in the conventional technology, the LED 6 is easily shifted in the direction T (the vertical direction in FIG. 11, and conveniently, referred to as the xe2x80x9clongitudinal directionxe2x80x9d) orthogonal to the longitudinal direction of the light conductive member 4, and the coupling efficiency is easily degraded, accordingly.
The present invention has been made in the light of the above problems, and an object of the present invention is therefore to provide a spread illuminating apparatus to improve the coupling efficiency between the light conductive member and the spot-like light source.
According to a first aspect of the present invention, there is provided a spread illuminating apparatus comprising a transparent substrate made of a light-transmissible material; a bar-like light source composed of a light conductive member made of a transparent material and formed bar-like and a spot-like light source disposed on at least one end of the light conductive member and mounted on a printed circuit board, and disposed close to and along at least one end of the transparent substrate; a frame having a plate-like main body disposed either under the printed circuit board or above the bar-like light source so as to oppose the printed circuit board, extending along the bar-like light source, and adapted to hold the transparent substrate and the bar-like light source; and a claw formed at an end of the main body so as to be in contact with the spot-like light source and adapted to press the spot-like light source toward the light conductive member.
According to a second aspect of the present invention, in the spread illuminating apparatus according to first aspect of the present invention, the spot-like light source has a recess in a face opposite to a face facing the light conductive member, and the claw is fitted in the recess.
According to a third aspect of the present invention, in the spread illuminating apparatus according to the second aspect of the present invention, the spot-like light source has solder applied to both end thereof positioned to be aligned in a direction orthogonal to a longitudinal direction of the light conductive member, and the recess is formed between the both ends so as to get clear of the solder.
According to a fourth aspect of the present invention, in the spread illuminating apparatus according to one of the second and third aspects of the present invention, the recess is groove-shaped and extends from one side of the spot-like light source, on which the main body is disposed, to the other side opposite to the side.
According to a fifth aspect of the present invention, in the spread illuminating apparatus according to one of the first to fourth aspects of the present invention, the frame is made of a springy material.
According to a sixth aspect of the present invention, in the spread illuminating apparatus according to one of the first to fifth aspects of the present invention, the spot-like light source is provided at each of both ends of the light conductive member, and the claw is formed at at least one end of the main body.
According to a seventh aspect of the present invention, in the spread illuminating apparatus according to one of the first to fifth aspects of the present invention, a spot-like light source is provided at one end of the light conductive member while a light reflection plate is provided at the other end thereof, one end of the main body is provided with the claw while the other end thereof is adapted to hold the light conductive member via the light reflection plate.
According to an eighth aspect of the present invention, in the spread illuminating apparatus according to one of the first to seventh aspects of the present invention, the spot-like light source is an LED.